The Southwest Oncology Group is a major multi-disease, multi- disciplinary, multi-institution group engaged in cooperative cancer research. This organization now consists of 33 Member Institutions, 21 Community Clinical Oncology Programs (CCOPs), 311 Cooperative Group Outreach Programs (CGOPs), 31 Urologic Cancer Outreach Programs (UCOPs), and 22 high priority affiliates, who together accrue over 6,000 patients to clinical trials each year. Currently there are approximately 105 studies open for accrual in 13 committees. The Statistical Center is essential to the design, conduct, and analysis of the cancer research in the Southwest Oncology Group. Its main functions are (1) to participate in the review of proposed protocols, particularly as regards experimental design, sample size, and feasibility; (2) to provide for central registration of all patients on all studies, and for randomization where appropriate; (3) to provide for review and quality control of data collected during studies; (4) to provide for data entry and computer processing, and storage and retrieval of data; (5) to work with the Group chair and other investigators in the Group to improve the quality of clinical trials through improved forms, more uniform and reproducible data definitions, and more economical flow of data, (6) to help the Group chair in the administration of the Group; (7) to analyze and publish the results of studies in conjunction with the study coordinator; (8) to use the data being collected to try to find new leads regarding prognostic factors and late effects; and (9) to perform statistical research on the efficient design, conduct, and analysis of cancer clinical trials and cancer control research.